Color filter is an important part of liquid crystal technology. The structure of color filter mainly includes a substrate, a black matrix (BM), a color film layer, a protective film layer (i.e., a flat layer) and a spacer film layer. Currently a color filter is still formed by proximity exposure process, position accuracy between film layers directly impacts on the quality of the color filter and even of the entire liquid crystal panel, in particular on the spacer layer, because in celling with TFT (Thin Film Transistor), its position often corresponds to the corresponding position of TFT, and there is a high demand for its accuracy. During operation, it is usually required to form an alignment mark through a mask plate in the formation of respective film layers as an alignment reference of automatic alignment between different film layers, between the spacer and the color filter as well as between the spacer and TFT. Generally, for a normal-size product (the size of a display area is smaller than the size of the mask plate), when exposed by each exposure unit, a group of alignment marks may be produced at its periphery (outside the display area) to precisely control the position accuracy of each member or film layer during each step. However, with the increase of the size of the product, there are more and more applications of splicing exposure techniques. For a supersized product (the size of the display area is larger than the size of the mask plate), the fabrication of its display area often needs to be completed by splicing exposure of a plurality of exposure units. Since the size of the mask plate is smaller than the size of the display area, it is not possible to produce the alignment mark located outside of the display area when exposed by each exposure unit. Therefore, it is not possible to precisely control the position accuracy of each member or film layer during each step, especially the position accuracy of the spacer. Moreover, when a position deviation (observed microscopically) occurs, it is not possible to measure in time and quickly compensate the position deviation.